Multiple cause mortality data will be employed in a study of urban/rural, size of place, and regional mortality differentials across demographically defined (e.g., race and sex) components of the U.S. population. The multiple cause data (data containing information on all medical conditions reported on the death certificate) will be particularly useful in assessing such geographic and demographic differentials at advanced ages where the prevalence of chronic disease is high, the frequency of multiply caused deaths is high and, consequently, underlying cause of death concepts and methods are inappropriate. The methods of mortality analysis to be applied are designed to be consistent with models of biological aging patterns and to reflect the effects of population heterogeneity on the comparison of mortality patterns across or within, national populations. These methods and analyses are also designed to reflect our knowledge of the reliability and validity of the death certificate diagnosis. Study will also be made of the detailed temporal variation of mortality rates to determine if the multiple cause data can be useful in explaining temporal patterns. The insight that will be gained into the substance of mortality by the use of multiple cause data and methods will be applied to the exploration of the effects of mortality changes on the rate of growth of the elderly population. The end product of this research will be to provide a basis for making more accurate predictions of the future elderly population using data derived from a period (1968-1978) characterized by rapid changes in mortality at advanced ages and where a complex mixture of disease specific changes in mortality contributed to mortality changes and demographic differentials in such changes.